The labor of childbirth is the process by which uterine contractions cause the fetus and placenta to be expelled from the uterus and birth canal. Rhythmic contractions of the uterine muscle create a force that pushes the fetus against the opening of the uterus, commonly referred to as the cervix. The cervix is a tubular structure that is firm and closed during pregnancy, keeping the baby and membranes protected inside the uterus. At term, the cervix softens and in labor the continuing pressure of the fetus on the cervix causes it to shorten (efface) and to open (dilate) up to 10 centimeters. As the cervix completely effaces and dilates, the contractions and the mother push the baby through the birth canal. The level of descent of the baby through this passage is referred to as station. Contractions are the forces that promote cervical dilation. Resistance of the cervix and the birth canal are the opposing forces to the contractions. In addition, the resistance of the cervix changes as it becomes more effaced and more dilated.
Commonly, the effacement, the dilation, the frequency and strength of the contractions and the station are measured clinically during labor and are used by the doctors to determine if the labor is progressing normally. Generally, if the doctor determines that the labor is progressing normally, the delivery is permitted to continue through the birth canal. However, if the doctor determines that the labor is not progressing normally, a cesarean section is effected to complete the delivery. Cesarean deliveries are associated with maternal morbidity and an increase in the risk of complications during the current and the subsequent pregnancies. Cesarean deliveries are also more expensive than vaginal births.
Due to the very large number of possible combinations of values for the dilation, the effacement, the frequency of the contractions and the station, the evaluation of labor progress is a difficult task for doctors. Unlike most surgical procedures, there is no suitable postoperative confirmation of the preoperative diagnosis that can be used to validate the doctor's decision.
One of the most commonly used guidelines for assessing the progress of labor during the first stage of labor is to evaluate the level of descent of the baby, or station, with respect to time. Intuitively, if the level of descent of the baby does not progress as time goes by, there may be cause for concern. Another guideline is to observe the dilation of the cervix during the first stage of labor with respect to time. Similarly, if dilation of the cervix does not progress as time goes by, there may also be cause for concern. For more information regarding the above, the reader is invited to refer to J. Zhang et al., “Reassessing the labor curve in nulliparous women”, Transactions of the twenty-second annual meeting of the society for maternal-fetal medicine, American Journal of Obstetrics and Gynecology, Volume 187, Number 4, October 2002, pp. 824-828. The contents of the above document are incorporated herein by reference.
A deficiency associated with existing methods, such as the ones described in the above noted publication, is that they do not adequately quantify labor progression. It will be appreciated that certain women take 4 hours to complete the first stage of labor while other women take 24 hours or more to complete the first stage. The above guidelines provide a general description of the average and range of observed rates of change in cervical dilation and fetal descent over time. These rates reflect an average response to an average set of conditions. They do not provide a method for discriminating if the unusually slow progression is due to conditions such as poor uterine contraction strength, or high cervical compliance or to a misfit between the size of the baby and the size of the mother. In practice, the clinical staff relies to a great extent on its knowledge and experience, rather than on such absolute measurements in order to make decisions as to whether an intervention should be considered. While doctors and nurses are trained and presumably competent in their ability to assess labor progression, there can be differences of interpretation that may result in either delayed or excessive rates of intervention depending upon the caregivers. As such, due to the lack of objective and reliable data, variations in judgment or management are more prone to occur; the more extreme causing harm to mother and or baby. Further, in the absence of such objective and reliable data and when the actions of the health care team are evaluated retrospectively, the reviewers who may be judges and jurors must also make subjective interpretations about the adequacy of the labor progression and the reasonableness of the clinical opinions at the time. The current methods do not provide a suitable indication of normal and abnormal labor progress, which considers specific and changeable labor conditions.
Therefore, in the context of the above, there is a need to provide a method and apparatus for providing information related to labor progress for an obstetrics patient that alleviates at least in part problems associated with the existing methods and devices.